As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FIRE DETECTOR INOPERATIVE LIGHT ILLUMINATED AFTER APU STARTED AND STABLE. ACFT GROUNDED. FOUND ENGINE & APU FIRE DETECTION MODULE M279 FAULTY. FOUND APU TAILPIPE OVERHEAT DETECTOR WITH HIGH RESISTANCE, 150 KOHMS. R & R M279 & APU TAILPIPE OVERHEAT DETECTOR M1925, IAW W/D 26-11-31 & MM'S 26-15-01 & 26-10-01. FIRE DETECTION OPS CHECKED NORMAL IAW MM'S 26-15-00 & 26-11-00.